1. Field of the Invention
The present invention concerns the use of alkyl and alkenyl glycosides and mixtures thereof with non-thio surfactants as collectors in froth flotation processes for the beneficiation of non-sulfidic ores.
2. Description of Related Art
Non-sulfidic minerals include, for example, apatite (3Ca.sub.3 (PO.sub.4).sub.2 CaF.sub.2), fluorite (CaF.sub.2), scheelite (CaWO.sub.4) and other salt-containing minerals, cassiterite (SnO.sub.2), titanium oxides, zirconium oxides, other metal oxides, certain silicates and alumo-silicates.
Froth flotation separation is a benefication technique commonly used in the mining industry for upgrading the valuable mineral content of ores. In preparation for flotation, the comminuted ore (the ore may be ground, either by dry-grinding but preferably by wet-grinding) is suspended in an aqueous medium, typically water. Collectors are normally added to the ore suspension, frequently in conjunction with frothers and optionally other auxiliary reagents such as regulators, depressors (deactivators) and/or activators, in order to facilitate separation of the valuable mineral constituent(s) from the unwanted gangue constituents. The comminuted ore suspension (or pulp) is conditioned by these reagents for a period of time before a gas, typically air, is sparged into the suspension to produce a foam which selectively floats an ore constituent on the surface. The collector is a hydrophobic agent which selectively coats the surface of the ore constituent, causing gas bubbles formed during sparging to adhere to the coated constituent. The remaining constituents of the ore which are not coated by the collector remain in the aqueous phase. In normal flotation processes, the ore constituent-containing foam is skimmed and collected for further processing. In reverse flotation processes the gangue constituent is floated and wasted while the aqueous concentrate is saved. In either type of flotation process, the object of the flotation is to separate and recover as much of the valuable mineral constituent(s) of the ore as possible in as high a concentration as possible.
Non-thio ionizable surfactants are a recognized class of flotation surfactants and are chiefly represented by the following compounds:
1. Alkyl carboxylate derivatives of carboxylic acid, such as fatty acids, RCOOH, and their sodium (RCOO.sup.- Na.sup.+) or potassium (RCOO.sup.- K.sup.+) soaps.
2. Alkyl sulfates, R--O--SO.sub.3 --Na.sup.+,(K.sup.+) and sulfonates R--SO.sub.3 --Na.sup.+,(K.sup.+).
3. Alkyl phosphates; both monoalkyl and dialkyl.
4. Amines, alkyl derivaties of ammonia, NH.sub.3, of which the primary amines RNH.sub.3 are used in flotation in the form of unsubstituted amine salts such as acetate, RNH.sub.3.sup.+ CH.sub.2 COO.sup.-, or hydrochloride or hydrobromide, RNH.sub.3.sup.+ Cl.sup.-, (Br.sup.-). The secondary amines, R.sub.1 R.sub.2 NH.sup.+ are used in flotation less often but together with the tertiary amines, R.sub.1 R.sub.2 NR.sub.3, are common emulsification agents, for example, dimyristylamine or dimethylmyristylamine. A modification of amine-type surfactants constitute the substituted amine salts, e.g., monoalkyl quaternary ammonium salts such as chlorides or bromides, RN(CH.sub.3).sub.3.sup.+ Cl.sup.-,(Br.sup.-), or dialkyl quaternary salts, R.sub.1 R.sub.2 N(CH.sub.3).sub.2.sup.+Cl.sup.- (Br.sup.-).
Other alkyl or aryl derivatives of amines are guanidine, piperidine, pyridine, cyclohexylamine and aniline (aminobenzene). Of the preceding derivatives the most frequently encountered are alkyl pyridinium salts.
As regards the class of hydrolyzable compounds, only those reagents with R groups containing between about 8 and 20 carbon atoms are employed in flotation; homologues shorter than C.sub.8 do not show enough surface activity, while homologues longer than about C.sub.20 become too insoluble for flotation purposes. The solutions of all these compounds are strongly affected by pH, giving rise to hydrolysis or dissociation, which strongly influences the surface activity by providing either the molecular or the ionic species. Also, all long-chain homologues of this class of reagents form aggregates (called micelles) when their solutions reach concentrations higher than a so-called critical micelle concentration (CMC) whenever their temperatures is above a certain minimum temperature called the Krafft point.
Many non-thio ionizable surfactants are known to be useful as collectors in the flotation of non-sulfidic ores. Known anionic non-thio ionizable surfactants include, for example, saturated and unsaturated fatty acids, particularly tall oil fatty acids and oleic acid, alkyl sulfates, particularly alkyl sulfates derived from fatty alcohols or fatty alcohol mixtures, alkyl aryl sulfonates, alkyl sulfosuccinates, alkyl succinamates and acyl lactylates. Known cationic non-thio ionizable surfactants include, for example, primary aliphatic amines, particularly the fatty amines derived from vegetable or animal and also certain alkyl-substituted and hydroxalkyl-substituted alkylene diamines and water-soluble acid addition salts of these amines.
Many surfactant collectors used to float non-sulfidic minerals inherently develop a foam suitable for flotation. However, it is frequently necessary or desirable to further develop or modify the foaming properties using special frothers. Known flotation frothers include C.sub.4 -C.sub.10 alcohols, polypropylene glycols, polyethylene glycol, polypropylene glycol ethers, terpene alcohols (pine oils) and cresyl acids. If necessary, modifying reagents, for example, pH regulators, activators for the desirable mineral constituents to be recovered in the foam or deactivators for the gangue constituents to be wasted in the underflow and possibly even dispersants may be added to the flotation suspension (pulp).
In contrast to anionic and cationic surfactants, nonionic surfactants are rarely used as flotation collectors. In Trans. Inst. Met. Min. Sect. C., 84 (1975), pp. 34-39, A Doren, D. Vargas and J. Goldfarb conducted flotation tests on quartz, cassiterite and chrysocolla using a collector comprising an adduct of 9 to 10 moles ethylene oxide with octyl phenol.
Collectors comprising a combination of an ionic and a nonionic surfactant have also been described in the relevant literature. A. Doren, A. van Lierde and J. A. de Cuyper report in Dev. Min. Proc. 2 (1979), pp. 86-109 carried out flotation tests on cassiterite with a collector comprising a combination of an adduct of 9 to 10 moles ethylene oxide with octyl phenol and an octadecyl sulfosuccinate. In A.M. Gaudin Memorial Volume edited by M/C. Fuerstenau, AIME, New York, 1976, Vol. I, pp. 597-620, V. M. Lovell describes flotation tests carried out on apatite with a collector comprising a combination of a tall oil fatty acid and nonyl phenol tetraglycol ether.
U.S. Pat. No. 4,526,696 to Delourme et al discloses a collecting composition, in the form of a micro-emulsion, for the froth flotation beneficiation of minerals. The minerals floated in the examples of this patent include a sulfide mineral of copper and a sulfided lead-zinc mineral. Other ores are mentioned in the patent specification. The collecting composition includes a collector, a liquid surfactant, a co-surfactant and optionally water. The collector is selected from organic compounds containing sulfur such as mercaptans, thioethers and polysulfides. As the liquid surfactant component, nonionic, cationic and anionic surfactants are mentioned, although nonionic surfactants are said to be preferred. Examples of nonionic surfactants mentioned in the patent include polyoxyalkylenes, esters and ethers of polyoxyalkylenes, polyoxyalkylene thioethers and alkyl glucosides. The co-surfactant component is typically an alcohol having 3 to 8 carbon atoms.
The cationic, anionic and ampholytic non-thio ionizable collectors that have been previously used for the flotation of nonsulfidic ores often do not permit satisfactory recovery of the valuable minerals when the collectors are used in economically feasible quantities. Accordingly, it is an object of the present invention to provide an economically feasible froth flotation process for the beneficiation of non-sulfidic ores. It is another object to provide a collector, for use in such flotation processes, with which it is possible to obtain either greater yield of valuable mineral using the same quantity of collector or the same yield of valuable mineral using a reduced quantity of collector.
A further object of the invention is to improve the efficiency of known primary collectors used for the flotation of non-sulfidic ores by adding thereto a co-collector according to the present invention in an amount such that the recovery of valuable mineral in the flotation process is significantly increased.